Voltage sensor housing and assembly including the same

ABSTRACT

A voltage sensor housing includes a top portion including a conductive top portion composed of conductive material and non-conductive top portions composed of non-conductive material, a bottom portion composed of non-conductive material, side portions composed of non-conductive material, wherein the top portion the bottom portion and the side portions define an interior area structured to hold a voltage sensor, and conductive side portions composed of conductive material and being disposed adjacent to the side portions. The conductive top portion is electrically floating and the conductive side portions are electrically grounded.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/583,882, filed Dec. 29, 2014, the contents of which are incorporatedin their entirety herein by reference.

This application is related to commonly assigned U.S. patent applicationSer. No. 14/583,880, filed on Dec. 29, 2014, (now U.S. Pat. No.9,733,281, issued Aug. 15, 2017), entitled “VOLTAGE SENSOR SYSTEM”, theentirety of which is incorporated herein by reference.

BACKGROUND Field

The disclosed concept relates generally to sensors housings, and moreparticularly, to voltage sensor housing. The disclosed concept alsorelates to voltage sensor assemblies including voltage sensor housings.

Background Information

Voltage sensors are used by power utilities to measure the voltage oftransmission lines, distribution lines, and busbars. The voltagemeasurements from these voltage sensors may be used as inputs to avariety of devices such as circuit interrupters. Some types of voltagesensors are inductive voltage transformers (IVTs), capacitive voltagetransformers (CVTs), and resistive dividers (RDs).

Some or all of IVTs, CVTs, and RDs suffer from the followinglimitations: a single sensor cannot measure AC and DC voltage; thesesensors require direct wiring to the circuit being measured; thesesensors cannot withstand normal and abnormal fluctuations in voltage;these sensors have poor stability over time and temperature; there ispower loss associated with these sensors; and some types of thesesensors require a special cooling system to remove heat generation dueto high power losses. A voltage sensor that can reduce or eliminatethese limitations would be desirable.

Voltage sensors are also susceptible to electromagnetic noise andinterference. It is desirable to reduce the amount of noise andinterference that reaches the sensor while allowing the sensor toperform its measurement. Sometimes a sensor alone is not sufficient toreduce noise and interference and a housing or enclosure is needed tofurther reduce noise and interference. However, there is room forimprovement in sensor housings and sensor assemblies including the same.

SUMMARY

These needs and others are met by embodiments of the disclosed concept,which are directed to a voltage sensor housing that includes aconductive portion that is grounded. These needs and other are also metby embodiments of the disclosed concept which are directed to a voltagesensor assembly that includes a voltage sensor and a voltage sensorhousing that includes a conductive portion that is grounded.

In accordance with one aspect of the disclosed concept, a voltage sensorhousing comprises: a top portion including a conductive top portioncomposed of conductive material and non-conductive top portions composedof non-conductive material; a bottom portion composed of non-conductivematerial; side portions composed of non-conductive material, wherein thetop portion the bottom portion and the side portions define an interiorarea structured to hold a voltage sensor; and conductive side portionscomposed of conductive material and being disposed adjacent to the sideportions, wherein the conductive top portion is electrically floatingand the conductive side portions are electrically grounded.

In accordance with another aspect of the disclosed concept, a voltagesensor assembly comprises: a voltage sensor including: a first plate; afirst electrode corresponding to and disposed a first distance away fromthe first plate; a second plate; and a second electrode corresponding toand disposed a second distance away from the second plate; and a voltagesensor housing including: a top portion including a conductive topportion composed of conductive material and non-conductive top portionscomposed of non-conductive material; a bottom portion composed ofnon-conductive material; side portions composed of non-conductivematerial, wherein the top portion the bottom portion and the sideportions define an interior area; and conductive side portions composedof conductive material and being disposed adjacent to the side portions,wherein the conductive top portion is electrically floating and theconductive side portions are electrically grounded, and wherein thevoltage sensor is disposed in the interior area of the voltage sensorhousing.

In accordance with another aspect of the disclosed concept, a voltagesensor housing comprises: a conductive top portion composed ofconductive material; a conductive bottom portion composed of conductivematerial; conductive side portions composed of conductive material,wherein the conductive top portion, the conductive bottom portion, andthe conductive side portions define an interior area structured to holda voltage sensor, wherein the conductive top portion, the conductivebottom portion, and the conductive side portions are electricallygrounded, and wherein two openings are formed in the conductive topportion.

In accordance with another aspect of the disclosed concept, a voltagesensor assembly comprises: a voltage sensor including: a first plate; afirst electrode corresponding to and disposed a first distance away fromthe first plate; a second plate; and a second electrode corresponding toand disposed a second distance away from the second plate; and a voltagesensor housing including: a conductive top portion composed ofconductive material; a conductive bottom portion composed of conductivematerial; conductive side portions composed of conductive material,wherein the conductive top portion, the conductive bottom portion, andthe conductive side portions define an interior area structured to holda voltage sensor, wherein the conductive top portion, the conductivebottom portion, and the conductive side portions are electricallygrounded, wherein two openings are formed in the conductive top portion,and wherein the voltage sensor is disposed in the interior area of thevoltage sensor housing.

BRIEF DESCRIPTION OF THE DRAWINGS

A full understanding of the disclosed concept can be gained from thefollowing description of the preferred embodiments when read inconjunction with the accompanying drawings in which:

FIG. 1 is a side view of a sensor system in accordance with an exampleembodiment of the disclosed concept;

FIG. 2 is a top view of a sensor from the sensor system of FIG. 1;

FIG. 3 is a side view of the sensor system of FIG. 1 employed inconjunction with a conductor;

FIG. 4 is a side view of a sensor system in accordance with anotherexample embodiment of the disclosed concept;

FIG. 5 is a top view of a sensor from the sensor system of FIG. 4;

FIG. 6 is an example of a square wave used in conjunction with thesensor systems of FIGS. 1 and 4;

FIGS. 7 and 8 are a side views of sensor systems employed in conjunctionwith a three phase power system in accordance with another exampleembodiment of the disclosed concept;

FIG. 9 is a simplified view of a sensor system employed in conjunctionwith a three phase power system in accordance with another exampleembodiment of the disclosed concept; and

FIGS. 10 and 11 are cross-sectional view of sensor assemblies includinghousings in accordance with example embodiments of the disclosedconcept.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Directional phrases used herein, such as, for example, left, right,front, back, top, bottom and derivatives thereof, relate to theorientation of the elements shown in the drawings and are not limitingupon the claims unless expressly recited therein.

As employed herein, the statement that two or more parts are “coupled”together shall mean that the parts are joined together either directlyor joined through one or more intermediate parts.

As employed herein, the term “number” shall mean one or an integergreater than one (i.e., a plurality).

As employed herein, the term “electrically floating” shall mean that acomponent is not electrically connected to a ground or other commonreference point in an electrical system.

FIG. 1 is a side view of a sensor system 1 in accordance with an exampleembodiment of the disclosed concept. FIG. 2 is a top view of a sensor 2from the sensor system of FIG. 1. FIG. 3 shows the sensor system 1 ofFIG. 1 employed in conjunction with a conductor 30. The circuitryassociated with the sensor 2 is shown in FIG. 1, but is not shown inFIGS. 2 and 3. However, it is contemplated that such circuitry may beemployed with the sensors 2 shown in FIGS. 2 and 3.

Referring to FIG. 1, the sensor system 1 includes the sensor 2 andassociated circuitry. The sensor 2 includes a first plate 10, a secondplate 12, a first electrode 14, and a second electrode 16. The sensor 2also includes spacers 18 that separate the first plate 10 from the firstelectrode 14 and the second plate 12 from the second electrode 16. Thefirst plate 10, the second plate 12, the first electrode 14, and thesecond electrode 16 are made of conductive material (e.g., copper, othermetallic materials, other suitable conductive materials, etc.), and thespacers 18 are made of a non-conductive material. Air gaps 20 aredisposed between the first plate 10 and the first electrode 14 and thesecond plate 12 and the second electrode 16.

In some example embodiments of the disclosed concept the plates 10,12and the electrodes 14,16 are substantially square and have an equallength 102 and width 104 (see FIG. 2). However, the disclosed concept isnot limited thereto. It is contemplated that the plates 10,12 an theelectrodes 14,16 may have any suitable shape. It is also contemplatedthat the plates 10,12 and the electrodes 14,16 may each have differentshapes and sizes. However, the plates 10,12 will generally have the samearea as each other. It is contemplated that the electrodes 14,16 may besmaller than the plates 10,12.

The circuitry associated with the sensor 2 includes a control unit 22,an inverting buffer 24, a differential amplifier 26, and any othersuitable circuit components such as capacitors and resistors. The firstplate 10 and the second plate 12 are electrically coupled to the controlunit 22. In more detail, an output of the control unit 22 iselectrically coupled to the first plate 10. The output of the controlunit 22 is also electrically coupled to the second plate 12 via theinverting buffer 24. The control unit 22 has two states. In the firststate, the control unit 22 electrically connects the first plate 10 toground and leaves the second plate 12 electrically floating. In thesecond state, the control unit 22 electrically connects the second plate12 to ground and leaves the first plate 10 electrically floating. Theinverting buffer 24 electrically connected between the first plate 10and the second plate 12 ensures that when one of the first plate 10 andthe second plate 12 is grounded, the other is electrically floating.

In FIG. 1, an electric field E incident on the sensor is shown. When thecontrol unit 22 is in the first state and the first plate 10 iselectrically connected to ground, the first electrode 14 is shieldedfrom the electric field E. The second plate 12, which is electricallyfloating, does not shield the second electrode 16, so the electric fieldE passes through the second plate 12 and induces a voltage in the secondelectrode 16. The induced voltage is directly proportional to themagnitude of the electric field E.

The first and second electrodes 14,16 are electrically connected to adifferential amplifier 26. The differential amplifier 26 outputs anoutput voltage V_(OUT) that is directly proportional to the differencebetween the voltage of the first electrode 14 and the voltage of thesecond electrode 16.

The electric field E may be an electric field that is created by currentrunning through a conductor 39 (see FIG. 3) such as a power distributionline or busbar. The magnitude of the electric field E is proportional tothe magnitude of the voltage in the conductor. Thus, by measuring thevoltage V_(OUT), the magnitude of the voltage in the conductor 30 can bedetermined.

When the electric field E is fluctuating, as it would be whenalternating current is flowing through the conductor 30, the controlunit 22 may remain in the first state, remain in the second state, orswitch between the first and second states. On the other hand, when theelectric field E is constant, as it would be when direct current isflowing through the conductor 30, the control unit 22 switches betweenthe first and second states. The reason for switching between the firstand second states is that over time a charge will build up on one of thefirst and second plates 10,12 that is electrically floating, which cancause the output voltage V_(OUT) to be inaccurate. Switching between thefirst and second states allows the first and second plates 10,12 to eachbe periodically electrically connected to ground. This allows charge tobe pumped into the circuitry (e.g., the differential amplifier) on aregular interval. Since a DC field is not changing, there would be nochange in induced charges in the electrodes 14,16 to measure. Switchingkeeps charges flowing, thus allowing the sensor 2 to measure DC voltagein the conductor 30.

The sensitivity of the sensor system 1 to measure voltage in theconductor 30 is based in part on the length of the gap 100 between theplates 10,12 and electrodes 14,16, the area of the electrodes 14,16, andthe distance 106 between the conductor 30 and the sensor 2. When thesensor system 1 is used in different voltage ranges, it may be suitableto adjust the sensitivity of the sensor system 1 to provide outputresults that are suitable for its application. For example, highersensitivity may be desired at lower voltage ranges and lower sensitivitymay be desired at higher voltage ranges. Since the sensitivity of thesensor system 1 can be adjusted by changing the distance 106 between theconductor 30 and the sensor 2, the sensitivity of the sensor system 1can be changed without physically changing the sensor 2, thus extendingthe range of voltages one sensor system 1 can be used to sense.

In one example embodiment of the disclosed concept, the length of thegap 100 between the plates 10,12 and electrodes 14,16 is about 10 mm,the area of the electrodes 14,16 is about 100 mm², and the distance 106between the conductor 30 and the sensor 2 is about 3 m. In anotherexample embodiment of the disclosed concept, the length of the gap 100between the plates 10,12 and electrodes 14,16 is about 20 mm, the areaof each electrode 14,16 is about 225 mm², and the distance 106 betweenthe conductor 30 and the sensor 2 is about 4 m. In yet another exampleembodiment of the disclosed concept, the length of the gap 100 betweenthe plates 10,12 and electrodes 14,16 is about 30 mm, the area of eachelectrode 14,16 is about 400 mm², and the distance 106 between theconductor 30 and the sensor 2 is about 5 m. In still another exampleembodiment of the disclosed concept, the area of each electrode 14,16 isabout 1 inch² and the length of the gap 100 between the plates 10,12 andelectrodes 14,16 is about 5 mm. In some other embodiments of thedisclosed concept, the distance between the conductor 30 and the sensor2 is about 1 inch, about 3 inches, or about 6 inches. It is noted thatthe aforementioned areas and distances are examples and the disclosedconcept is not limited thereto. Any suitable length of the gap 100between the plates 10,12 and electrodes 14,16, area of the electrodes14,16, and distance 106 between the conductor 30 and the sensor 2 may beemployed without departing from the scope of the disclosed concept. Gapdistances are inversely proportional to the dielectric constant of thematerial in the gap. Both the gap distance and the gap dielectricmaterial can be optimized for manufacturing, cost, size, and sensitivityas needed.

FIG. 4 is a side view of a sensor system 1′ in accordance with anotherexample embodiment of the disclosed concept. FIG. 5 is a top view of asensor 2′ from the sensor system 1′ of FIG. 4.

The sensor system 1′ and sensor 2′ of FIGS. 4 and 5 are similar to thesensor system 1 and sensor 2 of FIGS. 1 and 2. However, rather thanincluding spacers 18 and air gaps 20, the sensor 2′ of FIGS. 4 and 5includes a dielectric spacer 28 that is disposed between the first plate10 and the first electrode 14 and is also disposed between the secondplate 12 and the second electrode 16. The dielectric spacer 28 may bemade of any suitable dielectric material such as, without limitation,polymethyl methacrylate (PMMA). However, it is contemplated that anynon-electrically conductive dielectric material with a sufficiently highdielectric breakdown strength may be used, such as, without limitation,plastics, elastomers, ceramics, dielectric liquids, and epoxies.

It is contemplated that the sensor system 1′ and sensor 2′ of FIGS. 4and 5 may be used to measure the voltage in the conductor 30 (see FIG.3), similar to how the sensor system 1 and sensor 2 of FIGS. 1 and 2 areused to measure the voltage in the conductor 30.

FIG. 6 is a plot of an example square wave that may be output by thecontrol unit 22. As previously noted, the control unit 22 has a firststate in which the control unit 22 electrically connects the first plate10 to ground and leaves the second plate 12 electrically floating, and asecond state in which the control unit 22 electrically connects thesecond plate 12 to ground and leaves the first plate 10 electricallyfloating.

When the control unit 22 outputs the square wave of FIG. 6, the controlunit 22 first outputs a ground signal GND, which corresponds to thefirst state of the control unit 22. In more detail, the ground signalGND electrically connects the first plate 10 to ground. Since theinverting buffer 24 is electrically connected between the control unit22 and the second plate 12, the output of the control unit 22 isinverted, changing it from a ground signal GND to a floating voltageV_(CC) before it is applied to the second plate 12. Thus, the secondplate 12 is electrically floating in the first state. After apredetermined period of time t, the control unit 22 outputs the floatingvoltage V_(CC), which corresponds to the second state of the controlunit 22. In the second state, the control unit 22 applies the floatingvoltage V_(CC) to the first plate 10, which causes the first plate 10 tobe electrically floating. The inverting buffer 24 inverts the floatingvoltage V_(CC) to the ground signal GND before applying to the secondplate 12, which grounds the second plate 12. After another predeterminedperiod of time t, the control unit 22 switches back to outputting theground signal GND. The control unit 22 continues to switch betweenoutputting the ground signal GND and the floating voltage V_(CC) eachpredetermined period of time t. In some example embodiments of thedisclosed concept, the predetermined period of time t is significantlyshorter than an RC time constant of the sensor system 1 when measuringDC voltage in the conductor 30. When measuring AC voltage in theconductor 30, switching may not be required. However, if switching isused when sensing AC voltage in the conductor 30, the predeterminedperiod of time t should be significantly shorter than the period of theAC voltage.

FIG. 7 is a side view of the sensor system 1′ of FIGS. 3 and 4 employedin conjunction with a three phase power system in accordance withanother example embodiment of the disclosed concept.

The three phase power system includes first, second, and thirdconductors 40,40′,40″. The first conductor 40 is electrically connectedto the first phase P1 of the power system, the second conductor 40′ iselectrically connected to the second phase P2 of the power system, andthe third conductor 40″ is electrically connected to the third phase P3of the power system.

Three sensor systems 1′ are employed, each one corresponding to arespective one of the three conductors 40,40′,40″. Thus, the voltages ofthe conductors 40,40′,40″ can be determined from the output voltagesV_(OUT1), V_(OUT2), V_(OUT3) corresponding to the sensor systems 1′.Furthermore, the phases of the voltages of the conductors 40,40′,40″ canbe determined from the output voltages V_(OUT1), V_(OUT2), V_(OUT3)corresponding to the sensor systems 1′. Thus, the sensor systems 1′ canbe employed to monitor three phase power systems.

Although some of the circuitry associated with the sensors 2′, such asthe control unit 22 and the inverting buffer 24, is not shown in FIG. 7,it is contemplated that such circuitry may be included without departingfrom the scope of the disclosed concept. The sensor system 1′ of FIGS. 3and 4 is shown in FIG. 7, but it is contemplated that the sensor system1 of FIGS. 1 and 2 may also be employed in conjunction with the threephase power system of FIG. 7 without departing from the scope of thedisclosed concept.

FIG. 8 is a side view of the sensor system 1′ of FIGS. 3 and 4 employedin conjunction with a three phase power system in accordance withanother example embodiment of the disclosed concept.

The three phase power system of FIG. 8, similar to the three phase powersystem shown in FIG. 7, includes first, second, and third conductors40,40′,40″. The first conductor 40 is electrically connected to thefirst phase P1 of the power system, the second conductor 40′ iselectrically connected to the second phase P2 of the power system, andthe third conductor 40″ is electrically connected to the third phase P3of the power system.

Rather than using three sensor systems 1′ to sense the voltages in eachof the conductors 40,40′,40″, the arrangement in FIG. 8. uses one sensorsystem 1′ to sense the peak voltage in three conductors 40,40′,40″. Thesensor system 1′ provides the capability to sense the peak voltage andthe frequency content (e.g., harmonics) in the three conductors40,40′,40″ assuming that the conductors 40,40′,40″ are employed in abalanced system (i.e., equal phase voltages).

Although some of the circuitry associated with the sensors 2′, such asthe control unit 22 and the inverting buffer 24, is not shown in FIG. 8,it is contemplated that such circuitry may be included without departingfrom the scope of the disclosed concept. The sensor system 1′ of FIGS. 3and 4 is shown in FIG. 8, but it is contemplated that the sensor system1 of FIGS. 1 and 2 may also be employed in conjunction with the threephase power system of FIG. 8 without departing from the scope of thedisclosed concept.

FIG. 9 is a simplified view of the sensor system 1′ of FIGS. 3 and 4employed in conjunction with a three phase power system in accordancewith another example embodiment of the disclosed concept.

As shown in FIG. 9, three conductors 40,40′,40″ corresponding to thethree phases of the power system are arranged in a triangular pattern.Three sensor systems 1′ are employed. Each sensor system 1′ correspondsto one of the conductors 40,40′,40″. The sensor systems 1′ are disposedon the periphery of a circle around the conductors 40,40′,40″. Eachsensor system 1′ is located in the vicinity of its corresponding one ofthe conductors 40,40′,40″ so that it is closer to its correspondingconductor than to any of the other conductors 40,40′,40″. With thisarrangement, the sensor system 1′ can be used to conveniently sensevoltages in a three phase power system whose conductors are carried in asingle conduit.

The sensor system 1′ of FIGS. 3 and 4 is shown in FIG. 9, but it iscontemplated that the sensor system 1 of FIGS. 1 and 2 may also beemployed in conjunction with the three phase power system of FIG. 9without departing from the scope of the disclosed concept.

The sensor systems 1,1′ disclosed herein do not require an electricalconnection or physical contact with a conductor to sense the voltage ofthe conductor. Additionally, since the sensor systems 1,1′ shown anddescribed herein sense the voltage of the conductor based on theelectric field induced by the conductor, the sensor systems 1,1′ do notcause any power loss in the power passing through the conductor.Moreover, the sensor systems 1,1′ have the capability to sense AC and DCvoltage, and can be used over a wide voltage range.

FIG. 10 is a cross-sectional view of a sensor assembly in accordancewith another example embodiment of the disclosed concept. The sensorassembly includes a sensor 2, such as the sensor 2 shown in FIG. 1. Thesensor assembly also includes the circuitry associated with the sensor2. The associated circuitry is shown in FIG. 1, but is not shown in FIG.10. The sensor assembly also includes a housing 41.

The housing 41 includes an enclosed portion 42. The enclosed portionincludes sides 44,46, a top 48,50,52, and a bottom 54. Together, thesides 44,46, top 48,50,52, and bottom 54 define an interior space. Thesensor 2 is disposed in the interior space. The enclosed portion 42 maybe sealed so that the interior space is in a vacuum.

The top 48,50,52 of the enclosed portion includes a conductive topportion 48 and remainder portions 50,52. The conductive top portion 48is conductive and is electrically floating. This allows electric fieldsto pass through it. The remainder top portions 50,52, the sides 44,46,and the bottom 54 of the enclosed portion 42 are made of a differentmaterial. In some example embodiments of the disclosed concept, theremainder top portions 50,52, the sides 44,46, and the bottom 54 of theenclosed portion 42 are made of a non-conductive material. In someexample embodiments of the disclosed concept, the remainder top portions50,52, the sides 44,46, and the bottom 54 of the enclosed portion 42 aremade of, without limitation, ceramic, plastic, elastomer, or epoxy.

The housing 41 also includes conductive side portions 56,58. Theconductive side portions 56,58 are disposed adjacent to the sides 44,46of the enclosed portion 42. The conductive side portions 56,58 areelectrically grounded which prevents electric fields from passingthrough them.

The sensor assembly of FIG. 10 is effective in shielding the sensor 2from nearby conductors. For example, as shown in FIG. 10 the sensorassembly is disposed directly below a first conductor 60. The electricfield from the first conductor 60 is able to pass through the floatingconductor to the sensor 2 without being blocked by the conductive sideportions 56,58. Thus, the sensor 2 is able to sense the voltage in thefirst conductor 60. A second conductor 62 is disposed a lateral distancefrom the first conductor 60. Ordinarily, an electric field from thesecond conductor 62 could reach the sensor 2 and reduce the accuracy ofthe sensor's 2 voltage reading of the first conductor 60. However, theconductive side portions 56,58, which are grounded, block the electricfield from the second conductor 62 from reaching the sensor 2. Thus, thesensor 2 can accurately sense the voltage in the first conductor 60without interference from the electric field of the second conductor 62.

FIG. 11 is a cross-sectional view of a sensor assembly in accordancewith another example embodiment of the disclosed concept. The sensorassembly includes a sensor 2, such as the sensor 2 shown in FIG. 1. Thesensor assembly also includes the circuitry associated with the sensor2. The associated circuitry is shown in FIG. 1, but is not shown in FIG.11. The sensor assembly also includes a housing 70.

The housing 70 includes a conductive top 72, a conductive bottom 74, andconductive sides 76,78. The conductive top 72, bottom 74, and sides76,78 define an interior area. The sensor 2 is disposed in the interiorarea. The conductive top 72, bottom 74, and sides 76,78 are electricallygrounded which prevents electric fields from passing through them.

The conductive top 72 has two openings formed in it. The openingscorrespond to the first and second plates 10,12 of the sensor 2. Theopenings have a similar shape as the first and second plates 10,12 andare slightly larger than the first and second plates 10,12. The openingsallow electric fields from above the sensor 2 to reach the interiorspace, and in particular, to reach the first and second plates 10, 12and the first and second electrodes 14,16.

The sensor assembly allows the sensor 2 to sense the voltage of aconductor disposed above the sensor assembly. The conductive top 72,bottom 74, and sides 76,78 of the housing also block electric fieldsthat originate from other directions. This allows the sensor 2 toaccurately sense the voltage in the conductor by reducing general noiseand interference from other nearby conductors.

While the sensor 2 of FIGS. 1-3 is disclosed in use with the housings41,70 of FIGS. 10 and 11, it is contemplated that the sensor 2′ maysimilarly be employed in conjunction with the housings 41,70 of FIGS. 10and 11.

While specific embodiments of the disclosed concept have been describedin detail, it will be appreciated by those skilled in the art thatvarious modifications and alternatives to those details could bedeveloped in light of the overall teachings of the disclosure.Accordingly, the particular arrangements disclosed are meant to beillustrative only and not limiting as to the scope of the disclosedconcept which is to be given the full breadth of the claims appended andany and all equivalents thereof.

What is claimed is:
 1. A voltage sensor assembly comprising: a voltagesensor including: a first plate; a first electrode corresponding to anddisposed a first distance away from the first plate; a second plate; asecond electrode corresponding to and disposed a second distance awayfrom the second plate; and voltage sensor circuitry including: a controlunit structured to control one of the first plate and the second plateto be grounded and the other of the first plate and the second plate tobe electrically floating; and a differential amplifier electricallyconnected to the first electrode and the second electrode and beingstructured to output an output voltage that is proportional to adifference in voltage between the first electrode and the secondelectrode; and a voltage sensor housing including: a conductive topportion composed of conductive material; a conductive bottom portioncomposed of conductive material; conductive side portions composed ofconductive material, wherein the conductive top portion, the conductivebottom portion, and the conductive side portions define an interior areastructured to hold a voltage sensor, wherein the conductive top portion,the conductive bottom portion, and the conductive side portions areelectrically grounded, wherein two openings are formed in the conductivetop portion, and wherein the voltage sensor is disposed in the interiorarea of the voltage sensor housing.
 2. The voltage sensor assembly ofclaim 1, wherein the two openings formed in the conductive top portionare disposed above the first plate and the second plate, respectively.3. The voltage sensor assembly of claim 2, wherein each of the twoopenings is larger than the plate it is disposed above.
 4. The voltagesensor assembly of claim 1, wherein the first plate and the firstelectrode are separated by a first air gap and the second plate and thesecond electrode are separated by a second air gap.
 5. The voltagesensor assembly of claim 1, wherein the first plate and the firstelectrode and the second plate and the second electrode are separated bya dielectric material.